HOUSTON
— Lying atop a mountain of boxes inside a sweltering tractor-trailer  his face just inches from the ceiling  Luciano Alcocer said one final prayer before slipping into unconsciousness.

"I just kept thinking about my family in Mexico. Finally, I said, 'God, I'm in your hands now,' " says Mr. Alcocer from his temporary home in Dallas. The next thing the illegal immigrant remembers is the rush of air when the trailer doors were flung open  more than 12 hours after the harrowing ordeal began in West Texas.

Of more than 40 immigrants inside the unventilated trailer, two died  two more in a long summer of deaths along the USMexico border.

As the border has become ever more tightly guarded, illegal immigrants are increasingly forced to rely on wily smugglers  whose tactics often involve harrowing dangers while offering no guarantee of successful passage.

This summer, because of heightened security along the border since the terrorist attacks, immigrants are becoming more desperate to find ways to cross, and human smugglers are becoming more unscrupulous in their tactics.

"Since 9/11, we have seen a massive increase in the numbers of people paying to be smuggled into the United States," says Robert Fuentes, in charge of the Border Patrol's intelligence unit in Del Rio, Texas. "The fear of being apprehended is greater because of the influx of security and posturing on both the northern and southern border."

In fact, while the number of immigrant apprehensions is down by 28 percent over last year (translating into fewer attempted crossings), the number of rescues by the Border Patrol is up by 42 percent  suggesting that this summer has indeed been more dangerous.

And in some states, such as Arizona, it's been more deadly. Since January, there have been 141 immigrant deaths in Arizona  with the majority occurring in the summer months. There were just 102 in all of 2001.

The causes range from suffocation in trucks to heat exhaustion and dehydration in the desert. "The number of deaths in our sector are at an all-time high," says Robin Hoover, pastor of the First Christian Church in Tucson and president of Humane Borders, a relief organization that sets up water stations in the desert. "What is different is that the migrants, smugglers, and guides are moving farther west."

Farther west into the desert where there are fewer Border Patrol agents and less surveillance. Experts say smugglers  or coyotes  are having to find more remote, dangerous routes to remain undetected, but it also makes rescue attempts more difficult.

"These smugglers couldn't care less about human life. It's become big business," says Mario Villarreal with the Border Patrol in Washington. "The smuggling of human cargo now rivals that of drug smuggling."

For example, says Mr. Villarreal, smuggling fees in the 1980s and early '90s were between $50 and $100 a person. Now, coyotes are charging $1,000 to $2,000 a person. But with this fee increase has come little added benefit.

Some smugglers lie and tell immigrants a desert trek will be four to six hours when in fact it is three days or more. Some don't adequately inform immigrants of what to bring in terms of food, water, and clothing. Some abandon immigrants in the desert if they are unable to keep up.

IN Alcocer's case, this was his first trip to the US, and he says he hired a coyote to ensure that he would make it. He paid the coyote (whom he never saw) $1,600 for safe passage from Ciudad Juarez to Dallas.

After he crossed the Rio Grande, he waited for three days at a safe house near El Paso. Then, about midnight on July 26, a semi pulled up and loaded the group into the trailer with little water and no food. When some of the men protested, claiming they had been told they would ride in the cab, they were assured it was air-conditioned. As soon as the doors closed, the air became scarce and the heat intense.

When the truck successfully passed the checkpoint at Sierra Blanca  but did not stop  the men became desperate. They began banging on the inside of the trailer walls to alert attention. They opened the boxes in hopes of finding more water or food. Instead, the boxes of medical supplies contained plastic tubes that they jammed through cracks in the trailer to suck in fresh air.

More than 12 hours later, they were rescued after passing motorists saw the tubes, as well as some of the men's belts, sticking out of the trailer. The immigrants are being allowed to stay in the US while the case against the smugglers goes forward. A conviction could result in the death penalty.

The government is prosecuting smugglers in increasing numbers, and judges are handing down stiffer sentences. In February, Border Patrol agents in Sarita, Texas, found 78 immigrants stuffed into the trailer of a semi. The driver pleaded guilty to transporting undocumented immigrants and received 10 years in prison.

Back in the Del Rio sector, the first three cases against smugglers who are charged with immigrant endangerment are working their way through the courts. One involves a smuggler who tried to escape the authorities and rolled a vehicle containing four immigrants. One died.

"These prosecutions really show that we are really cracking down on the smuggler and want to send a message that if you endanger people's lives, we are going to take action against you," says Mike DeBruhl, an assistant chief in the Border Patrol's Del Rio sector.

The Rev. Dr. Hoover, of Humane Borders, argues against the portrayal of smugglers and guides as evil. "What you see is a concerted effort on the part of the US government to demonize the coyote," he says. "But US border policies have created the smuggling industry. And putting more pressure on existing migrant routes [sends] migrants to more dangerous areas."

For his part, Alcocer of Mexico City says he will never use another. "It was an experience that is going to haunt me for the rest of my life," he says, "and I wouldn't wish it on anyone else."